Science diplomacy is coming to the fore as a formidable dimension of interstate power relations. As the challenges of the world increasingly transcend borders, so too have researchers and innovators forged international coalitions to resolve global pathologies. In doing so, new channels of influence and opportunity have opened up for states alongside the ‘traditional’ modes of foreign diplomacy. Understanding how these channels influence global socio-economic outcomes is thereby crucial for scholars interested in the still-ambiguous structure and processes of global governance. This article advances understanding of the domains of science diplomacy by drawing attention to the ‘political intercostalities’ of state actors, scientific communities and other transnational actors within the new architectures of global governance. Here we trace the growing array of informal international associations alongside transgovernmental policy networks and ‘global public-policy partnerships’ that deal with highly specialised and technical matters of international policy and how they are drawn into science diplomacy. This article thus presents a research agenda for a particular mode of ‘impact’ in politics and international studies.